Login failed for user 'IIS APPPOOL\myAppPool

If you don't change, each app pool has it's own identity. In your case, just add a new user to your database SmallBakery with the name IIS APPPOOL\MyAppPool using SQL Management Studio. You find the users list in the "Security/Users" subnode of your database. This should look something like that:

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For testing, let the user be member of the db_owner role. If that works, remove this role and just let it be member of db_datareader and db_datawriter.

This way, each app pool (perhaps each website, if they all use their own app pool) only has access to the corresponding database.